Reference

Plot basics

All ggplot2 plots begin with a call to ggplot(), supplying default data and aesthethic mappings, specified by aes(). You then add layers, scales, coords and facets with +. To save a plot to disk, use ggsave().

Layer: geoms

A layer combines data, aesthetic mapping, a geom (geometric object), a stat (statistical transformation), and a position adjustment. Typically, you will create layers using a geom_ function, overriding the default position and stat if needed.

Scales

Scales control the details of how data values are translated to visual properties. Override the default scales to tweak details like the axis labels or legend keys, or to use a completely different translation from data to aesthetic. labs() and lims() are convenient helpers for the most common adjustments to the labels and limits.

Guides: axes and legends

The guides (the axes and legends) help readers interpret your plots. Guides are mostly controlled via the scale (e.g. with the limits, breaks, and labels arguments), but sometimes you will need additional control over guide appearance. Use guides() or the guide argument to individual scales along with guide_colourbar() or guide_legend().

Themes

Themes control the display of all non-data elements of the plot. You can override all settings with a complete theme like theme_bw(), or choose to tweak individual settings by using theme() and the element_ functions. Use theme_set() to modify the active theme, affecting all future plots.

Extending ggplot2

To create your own geoms, stats, scales, and facets, you’ll need to learn a bit about the object oriented system that ggplot2 uses. Start by reading vignette("extending-ggplot2") then consult these functions for more details.

Autoplot and fortify

autoplot() is an extension mechanism for ggplot2: it provides a way for package authors to add methods that work like the base plot() function, generating useful default plots with little user interaction. fortify() turns objects into tidy data frames: it has largely been superceded by the broom package.